A Body Area Network, called BAN is a network attached to the human body, which is composed of a set of small and movable sensors with communication function and a body master station (central device). Each sensor can be worn on the body or implanted inside the body. A wireless body area network is a short-range wireless communication network applied on body surface or inside the body, and is mainly used for the monitoring of biological signs information and other wireless applications. The wireless body area network is composed of various medical sensor nodes and a hub node all over the outside and the inside of the body. The sensor may be, for example, an electrocardiogram sensor, a heart rate sensor, a blood pressure sensor or a temperature sensor, etc.
The hub node is responsible for collecting physiological data acquired by sensor nodes, which are used for physical examination and an analysis and prediction of the disease, etc. This medical application based on the wireless body area network greatly facilitates users and hospitals and saves medical costs at the same time. In addition to typical medical applications, the wireless body area network may also be used for monitoring physiological parameters of an athlete so that the athlete can carry out effective training according to the corresponding parameters; the wireless body area network may also be used in military to know about the physical status of soldiers on the battlefield in time. The IEEE has published a first standard for the WBAN (IEEE 802.15.6) in March, 2012.
The sensors for medical applications are usually attached on the body surface or implanted into the body, and since the human body comfort and the difficulty of the implantation into the body are considered, this type of sensors are all miniaturized, thus the battery capacity for a sensor is limited. Some sensors might be required to work for a few years or even decades, and it is a severe challenge how to reduce power consumption and prolong service life of a sensor node as much as possible. In addition, when a sensor sends data packets to the hub node, the wireless link becomes unstable due to the particularity of human body environment and human movement characteristics, and it is another problem faced by the wireless body area network technology how to reliably transmit data is another problem.
Further, Media Access Control, called MAC layer controls when various sensor nodes access the channel and perform a receiving/sending data packets operation, thus MAC layer also relates to the power consumption and data transmission of a wireless body area network. In view of this, low power consumption, low latency and reliable transmission become an urgent problem to be solved in wireless body area network applications.
In related arts, a super-frame structure based on a Beacon mode is given in IEEE 802.15.6 standard protocol, as shown in FIG. 1. The frame begins with a Beacon and is composed of: an Exclusive Access Phase 1 called EAP1, a Random Access Phase 1 called RAP1, a Managed Access Phase 1 called MAP1, an EAP2, a RAP2, an MAP2, a Beacon 2 and a Contention Access Phase called CAP, herein:
The EAP is a phase specially used for emergency service packets transmission, and adopts CSMA/CA or time slot ALOHA which is a competitive mechanism. The RAP and CAP are phases used for ordinary service packets transmission, and adopt CSMA/CA or Slotted ALOHA which is a competitive mechanism. The MAP is a phase used for emergency service/ordinary service transmission, and adopts access modes based on the “Scheduling” and the “Polling”. If a CAP phase needs to be used, the hub node will notify sensor nodes through the Beacon2, called B2.
In the IEEE 802.15.6, conflicts can be avoided in the transmission process since the MAP phase is operated by the ways of “Scheduling” and “Polling”, but the disadvantage is that: the MAP requires that the hub node and the sensor node carry out a series of “query-response” and this process brings additional interactive energy consumption. There are two parts of MAP phase in the standard protocol, and since the MAP phase is carried out by the way of “Polling”, the communication module of each sensor node has to be opened so that the hub node polls to the communication module of each sensor node, which can bring additional power consumption, and the time delay for data transmission is longer.
The above is merely used to help to understand the technical solution of the present document and does not mean to admit that the above is the existing art.